In numerous operations it is necessary to temporarily plug an open-ended tube, particularly for leak testing the same, which has an inaccessible end or which end can only be accessed with great difficulty or with the expenditure of substantial amounts of time to disassemble the device containing the tube. This is particularly true when leak testing tube and shell type heat exchangers particularly tube and shell type heat exchangers having at least one floating head. Such heat exchangers are extensively utilized in industry particularly in the petroleum refining industry. Such a heat exchanger is illustrated in FIG. 17-7 at page 546 of "Petroleum Refinery Engineering", W. L. Nelson, 4th Edition, McGraw-Hill, 1958, which illustration is incorporated herein by reference.
Due to the inherent construction of such heat exchangers and the severe conditions to which they are exposed during use, leaks will develop which must be located and repaired. The difficulty of locating such leaks is clearly apparent from FIG. 17-7 of the Nelson reference and FIG. 2 of the drawings of the present application. It is to be seen that the tube bundle is formed by fixedly mounting the tubes in a stationary tube sheet and a floating tube sheet, the latter permitting expansion and contraction of the bundle of tubes. The end having the stationary tube sheet as covered by the channel cover and the end having the floating tube sheet is covered by both a floating head cover and a shell cover. Thus, in order to acess the open end of the tubes it is only necessary to remove the channel cover on one end but it is necessary to remove both the floating head cover and the shell cover on the end having the floating tube sheet. The structure of the device also makes it apparent that, if a leak does develop, it is most likely to develop at one of a multiplicity of potential points in the end having the floating tube sheets. Most likely points of leakage are the lowermost tubes themselves and the floating head, particularly the floating head gasket. Obviously one can not determine, from inspection of the exterior of the exchanger, which of these elements is leaking, whether it is a tube or the head itself. When the leak is observed, it is common practice in the art to remove the shell cover and the floating head to either grease the tube sheet or plug the end of suspected tubes, reinstall the floating head and shell covers and apply pressurized fluid on the shell side of the exchanger. If after this test one is able to distinguish between a leaking head and a leaking tube and determine that a tube is leaking it will once more be necessary to remove the shell cover and the floating head cover and plug the tube suspected of leaking. Unfortunately, one is seldom able to distinguish between a floating head leak and a tube leak on the first test and it is generally necessary to repeat this disassembly and reassembly procedure three to four times in order to arrive a reliable conclusion and remedy the situation. This prior art procedure is quite time consuming irrespective of the skill of the tester.
It would therefore be highly desirable if blind tube ends could be conveniently plugged without major disassembly and uncertainty in the testing of the tube for leaks.